Problem with gategory ID

Hi

i’m trying to use plugin, i create a category and i associate this to a page and many posts. In my page i want page content and posts with the same category. I make this

$cat = get_query_var(‘cat’);
$argsText = array(‘category’ => $cat, ‘numberposts’ => -1, ‘post_status’ => null, ‘post_type’ => ‘post’);

$postsText = get_posts( $argsText );

But $cat is empty. How can i get the category id of current page??
Help me please!

http://ww.wp.xz.cn/plugins/post-tags-and-categories-for-pages/